T.
K.,
The way to know for sure is to see your OB/Gyn. I've miscarried twice and basically they did a blood test for pregnancy hormones. They did at least 2 with at least 2 days in between them to make sure the hormones were dropping appropriately. They kept doing that until my pregnancy hormones were back at a normal level. If you are trying to get pregnant you might want to ask for a referral to a reproductive endocrinologist. They can help you identify why your hormones are all out of whack (and if you aren't having regular periods, your hormones are out of whack) and hopefully help you fix it.
T.